The present invention is directed to the preparation and use of novel recombinant DNA molecules in which an avian long terminal repeat (LTR) is ligated to the bovine growth hormone (BGH) gene. Stable mouse fibroblast cell lines have been generated which contain the recombinant genetic material integrated into the mouse cell genome, and which are valuable for production of large amounts of biologically active BGH.
U.S. Pat. No. 4,405,712 describes the use of the LTR vector for activating the expression of a desired gene. Activation is achieved by (1) isolating tee desired gene; (2) ligating to the gene a vector comprising the LTR sequences from a retroviral provirus genome, thus providing a hybrid gene; (3) inserting the hybrid gene into a mammalian recipient cell using DNA transfection; and (4) screening the cells for the phenotype of the gene. The LTR vector can be linked to the gene of interest by conventional recombinant techniques and serves as a marker for identification and cloning of the gene by standard recombinant DNA cloning procedures.
The cloning and sequencing of the bovine growth hormone gene is described in the article Woychik et al., Nucleic Acids Research, Vol 10, Nov. 22, 1982, pp. 7197-7210, see also Keshet et. al., Nucleic Acids Research, Vol 9, Nov. 1, 1981, pp. 19-30. The nucleotide sequencing of a variety of avian retroviral LTRs is described by Bizub, Katz and Skalka, J. Virology, 49:557-565, Feb. 1984.